Controllers for split-phase electric motors



Oct. 31, 1961 R. H. TEASELL 3,007,062

CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Filed July 5, 1957 3Sheets-Sheet 1 Inventor Ems/ALB 19. 72945:

Attorney Oct. 31, 1961 T sELL 3,007,062

CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Filed July 5, 1957 3SheetsSheet 2 l v. i 4Z .J Inventor EONALDH 7Z=AsEL L Attorney Oct. 31,1961 R. H. TEASELL 3,007,062

CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Filed July 5, 1957 3Sheets-Sheet 5 Attorney United States Patent 3,007,062 CONTROLLERS FORSPLIT-PHASE ELECTRIC MOTORS Ronald Harold Teasell, North Wembley,England, as-

signor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Filed July 5, 1957, Ser. No. 670,278 Claims priority,application Great Britain July 10, 1956 12 Claims. (Cl. 307-112) Thisinvention relates to starting controllers, that is starting relays, forsplit-phase electric motors.

The function of such controllers is to ensure that the motor starts withboth the main (i.e. the running) winding and the phase (i.e. thestarting) winding energised, and that the phase winding is switched out,responsive to a current flow in the main winding, when the motor hasreached a suitable speed.

Such controllers must respond to two current conditions in the mainwinding:

(a) The current flowing through the main winding whilst the motor is ata standstill, which must operate the connection of the phase winding,and

(b) The current existing when the motor is running with both windingsconnected at a balanced speed condition, and from the decay of whichcurrent there results the disconnection of the phase winding.

By the use of the present invention, starting controllers may be madewhich will function even when the current differential, that is thedifference between quantities (a) and (b), is very small; suchcontrollers render the motor operable with widely different supplyvoltages and load conditions.

The scope of the invention is defined by the appended claims; how theinvention may be performed is particularly described below Withreference to the accompanying drawings, in which:

FIGURE 1 is an enlarged plan view of the starting controller deviceremoved from a case;

FIGURE 2 is a perspective view, enlarged, of part of the device shown inFIGURE 1;

FIGURE 3 is a circuit diagram showing the device of FIGURES l and2-connected to the motor; and

FIGURE 4 is a plan view of a modified device.

Referring to FIGURE 1 the controller there shown has a moulded phenolicbase 1 to which is spun an extrusion from a terminal strip 2, bentupwards to form a contact face by means of a silver inlay 3. This makescontact with a silver contact 5, Welded to a bimetal strip 4, which isformed at right angles and attached to a raised portion 6 of the base byan eyelet 17. This strip 4 is retained by a slot 18 which preventsmovement during operation of the bimetal. Adjustment of the bimetalstrip 4 is made by a slotted grub screw 62 which is located in theraised portion of the base 6. The eyelet 17 further retains a heaterwire 7, which is formed in coils 19 alongside the bimetal strip 4, andretained on a steel bracket 9 secured to the base 1. To provide a soundelectrical joint the heater wire is looped around eyelet 10. Two brasseyelets 10 and 11 retain the steel bracket 9 to the base 1, and thebracket is formedupwards to form a stop 20 which can be adjusted toposition the bimetal strip 4. This strip is normally positioned with thecontacts 3, held in the closed position by a steel toggle spring 12which exerts a force from its position 21 on the Strip 13, which is abimetal compensator against ambient temperature variations. Thiscompensator is mounted to the base on a raised leg 16 by means of twoeyelets 14 and 15, and is further retained by a ledge 22.

The lower raised end 23 of the steel bracket 9 is formed 3,007,062Patented Oct. 31, 1961 "ice to provide a mounting, upon which is weldedthe arm 24A of a U-shaped bimetal strip 24 carrying a silver contact 25riveted to the end of the other arm 24B. An eyelet 26 riveted to thecentre of the U carries a flexible lead 27, soldered at the opposite end28 to the end of a berylliumcopper blade 29' about .005 thick (seeFIGURE 2). Facing the bimetal contact 25 is a silver contact 30 rivetedto a Phosphor bronze blade 31, about .006 thick, held to the base by aneyelet 32 and retained at the end by a slot on the base 33. The eyelet32 also retains a brass terminal tag 34 to which is soldered the end ofa solenoid coil lead 35. The Phosphor bronze strip 31 is formed toprovide a projecting finger 36 reaching into the bore of the solenoidbobbin 37, and this strip is normally positioned to ensure that thecontacts 25, 30 are approximately .030" apart. The solenoid bobbin 37 isheld in position to the base 1 by pillars 3-8, 39, 40, which prevent thecoil moving up or down, and is further retained by a locking pin 41which passes through the bobbin. Inside the bore of the solenoid bobbinrests an iron armature slug 42, which is cylindrical, smooth and roundedat the edges to permit free operation movement inside the bore of thesolenoid bobbin.

The slug 42 is positioned by an adjustable stop screw 43, consisting ofa screw 43 of insulating material which can be moved through a threadedpillar 44 to move the slug into the bore. The slug 42, by virtue of itsweight, presses a springy contact blade 29, 45 against the stop screw43, keeping a contact 46, which is riveted to the beryllium copper strip29, in the open circuit position. The strip 29 is formed such thatcontact 46 would press against a contact 47 and make electrical contact,were the weight of the slug 42 not applied to the end 45 of the strip.Contact 47 is riveted to a brass bracket 48 which has an extrusion 49spun to the base 1. The beryllium copper strip 29 is riveted to a pillar50, projecting from the base 1, by an eyelet 51 before extending to asoldering point 28 where both the flexible lead 27 and a solenoid coillead 52 are soldered to make electrical contact. The coil lead 52commences the solenoid coil 53 wound around the bobbin 37, and which istapped by extending a loop 54 soldered to a terminal tag 34 at a point35, as shown in FIGURE 1. The end of coil 53 is brought from the lowerend of the bobbin at 55 and is soldered to a terminal strip 56, which isspun to the base 1 by an extrusion 57. Five wiring points are made bytapping the extruded tags 2, 49, 57, and nuts and screws 5859 and 60-61.

Referring to FIGURE 3 which is a wiring diagram of the motor and controlcircuit, a switch is mounted in the supply line and closure of thecontacts 71 and 72 connects a circuit through the starting relay i.e.,the controller described above, through the main winding 74 of the motor75 and back to neutral. This current flows through the contacts 3 and 5and along the bimetal strip 4, which increases in temperature as aresult of its resistance and through the heater coil 19. It then flowsthrough the bracket 9, through the thin leg 24A of the U-shaped bimetalstrip 24 which increases in temperature as a result of its resistance,through the solenoid coil 53 from end to end, and into the main winding74 of the motor. This current flow, is sufficient to create a flux inthe solenoid coil 53 which attracts the slug 42 into the coil, and thismovement allows the switch formed by the contacts 46 and 47, to closeand connect the phase winding 85. As the slug 42 is pulled to the centreof the coil 53 it strikes the projecting finger 36 and forces theconand, together with a decrease in current as the motor 3 acceleratesand a downward force applied by the finger 36 of the blade 31 (which maybe called the armaturereturning blade), the slug is dropped clear of thecoil 53.

As the slug 42 is dropped clear and the finger 66 is released, thecontacts 25 and 30 are held temporarily to the closed position by thethermal deformation of the bimetal strip 24, the thin arm 24A of whichhas flexed as a result of the current and the resistance of the strip.The slug 42 opens the contacts 46, 47 thus disconnecting the phasewinding 85. The low current which exists when the motor is runningnormally allows the contacts 25, 30 to separate and the relay is then ina position to re-start the motor when required. The current flow throughthe overload bimetal strip 4 and the heater 19 whilst the motor isstarting, does not remain for a sufficient time to flex bimetal strip 4appreciably, but should the motor run on an overload or fail to startcorrectly, the current flow through these parts creates sufficient heatand, therefore causes flexure of the bimetal 4 to separate the contactsand 3' by the snap action of toggle spring 12, and disconnect thevoltage supply. These will normally reset after a short interval of timeand the motor will then attempt to re-start.

FIGURE 4 shows a modified and somewhat simple starting controller, whichis substantially the same as the one according to FIGURES l-3 exceptthat the U-shaped bi-metallic strip 24 is omitted, and the Phosphorbronze spring blade 31 is replaced by a thin bi-metallic springy blade31A. This is fixed to a steel bracket 9A (corresponding to bracket 9)and at starting carries the combined current flowing in the main andphase windings. To the end of the blade 31A is fixed a copper rivet 36Aforming a finger adapted to be struck by the attracted armature slug 42.A flexible copper lead 27A (compare lead 27 in FIGURE 1) connects rivet36A to a point 28A (compare 28 in FIGURE 1) on a U-shaped metal bracket50A. At 28A the circuit divides, the current to the main winding passingby the wire 52 to the solenoid winding (compare description of FIGURE1), and the current to the phase winding passing through the bracket 50Ato the beryllium-copper blade 29A (equivalent to the blade 29 in FIGURE1), fixed by rivets 29B. The remaining parts are substantially the sameas the corresponding parts in FIGURE 1, and have the same referencenumerals as those parts. 44A is a stop corresponding to the adjustablestop screw 44 in FIGURE 1.

The action on starting is that current flows through the over-loadheater 19 to the bracket 9, through the bi-metal blade 31A, along theflexible lead 27A, to bracket 50A, through lead 7 and around thesolenoid coil 53, leaving it by lead 55 which connects to the mainwinding by terminal bracket 56. The current flow through coil 53 resultsin a flux which attracts the armature slug 42 upwards allowing theberyllium-copper strip 29A to move upwards, so that the phase-windingswitch formed by contacts 46, 47 is closed. Thus both motor windings areenergized. The slug 42 strikes the copper rivet 36A and thus appliespressure to the bi-metal blade 31A which is deflected slightly upwards.The slug 42 then commences to move back towards the centre of thesolenoid bobbin acting under the force of gravity, the spring deflectionof the bi-metal blade 31A, and the downward flexure of the bi-metalresulting from its temperature rise due to the current flow. Thisaugments its spring force. At this moment the motor, which has beenaccelerating, will apply a decay of current though the main winding andthis also will assist in allowing the slug to drop clear of the bobbin.The slug will then strike the end 45A of the beryllium-copper blade 29Aand open the contacts 46, 47 controlling the phase winding. If the slug42 should fail to leave the bobbin cleanly, the bi-metal blade 31A willcontinue to deflect downwards and the copper rivet 36A will force theslug into a position at the lower end of the coil, the relative positionof which decreases the current required to hold the slug into thebobbin.

I claim:

1. A starting controller for an electric motor, including in thecombination, an electrically energizable solenoid, an armature attractedto the solenoid by energization of the solenoid, a switch forcontrolling an electric circuit including spring means urging the switchtoward closed position, said switch being normally held open by thegravity applied weight of the armature as unattracted to the unenergizedsolenoid and closed by the spring means when the armature is attractedto the solenoid when energized, and an armature return spring meansnormally disengaged from the armature when the solenoid is unenergizedbut engaged by said armature in solenoid attracted position with thesolenoid energized thereby to partially oppose the attracting force ofthe solenoid by the force of said spring means to spring aid therebygravity release of the armature from the solenoid on decay of electriccurrent in said solenoid.

2. A starting controller including the structure set forth in claim 1wherein said spring means is thermally sensitive and electric currentresponsive and in series circuit with said solenoid to increase therebythe spring effectiveness of said spring means during energization ofsaid solenoid.

3. A starting controller including the structure set forth in claim 1wherein said spring means is thermally sensitive and electric currentresponsive and is in series circuit with said solenoid and has oneposition with the solenoid de-energized and a second position with thesolenoid energized to increase thereby the spring effectiveness of thesaid spring means during energization of said solenoid.

4. A starting controller for an electric motor, including in thecombination, a fixed contact, a movable contact closable on the fixedcontact and adapted to close an electric circuit, a spring blade bearingsaid movable contact and urging it toward closure with said fixedcontact, an electrically energizable solenoid having a hollow borelocated above the free end of said blade, a loose armature in saidsolenoid bore normally resting its gravity applied weight on the end ofsaid blade to hold said movable contact away from said fixed contact,said armature being adapted to be lifted from said blade by energizationof said armature to permit said movable contact to close on said fixedcontact, and an armature return spring blade located above said solenoidnormally disengaged from said armature and adapted to be engaged andbent by the said armature when in attracted position by energization ofsaid solenoid to exert thereby a spring force operating against thearmature attracting force to spring aid gravity release of the armaturefrom the solenoid on decay of electric current in said solenoid.

5. A starting controller constructed and arranged in accordance with thestructure set forth in claim 4 wherein said spring blade is a bimetalelectric current sensitive member in series circuit with said solenoidto bend under the heating effect of electric current passing to saidsolenoid to increase thereby its armature returning force in proportionto the current flowing through said solenoid.

6. A starting controller constructed and arranged in accordance withclaim 1 wherein said spring means is thermally sensitive and electriccurrent responsive and is in series circuit with said solenoid toincrease thereby the spring effectivenessof the said spring means duringenergization of said solenoid to spring aid thereby gravity release ofthe armature from the solenoid on decay of electric current in saidsolenoid, and wherein said spring means includes a second switch circuitconnected with said solenoid to short circuit a part of the solenoidwhen said second switch is closed by attraction of said armature toreduce thereby the flux eifect holding the armature in attractedposition.

7. A starting controller for an electric motor constructed and arrangedaccording to claim 1 that includes a short circuiting switch in seriescircuit with said solenoid to short circuit a part of said solenoid whenclosed and includes a thermally deformable element actuating said shortcircuiting switch as heated by the eifect of current flow to thesolenoid, said thermally deformable element holding the short'circuiting switch temporarily closed when the armature is released.

8. In a starting controller, an electrically energizable solenoid, anarmature attracted by energization of the solenoid, a switch forcontrolling an electric circuit including spring means urging the switchtoward closed position, said switch being normally held open by gravityapplied weight of said armature to said spring means when unattracted bythe solenoid and closed by said spring means when said armature isattracted by energization of said solenoid to remove the gravity appliedweight of the armature from the spring means, and an armature returnspring in the form of an electric current sensitive bimetallic bladeelectrically in series with the solenoid and electrically in series withthe said switch to conduct thereby the combined currents conducted tothe said solenoid and to the circuit containing the said switch, saidarmature being normally disengaged from said return spring whenunattracted by said solenoid and engaging said return spring whenunattracted by said solenoid, said return spring deforming under theheating eifect of the combined currents flowing through the same tospring aid thereby gravity release of the armature to open said switchon decay of current flow through the solenoid and the circuit containingsaid switch, said solenoid continuing to receive current through saidbimetallic blade after opening of said switch by said armature with thecurrent flow thereby through said bimetallic blade being reduced by thevalue of the current removed upon opening of said switch.

9. Apparatus constructed and arranged in accordance with claim 8 whereinsaid armature return spring includes a short circuiting switch closableby the attraction movement of the armature to the solenoid to shortcircuit a part of the solenoid whereby to reduce the flux effect of thesolenoid on the armature in attracted position.

10. Apparatus constructed and arranged in accordance with claim 8wherein said solenoid has a hollow bore with said armature movable insaid bore, said armature return spring having a finger projecting intothe bore of said solenoid in the path of the armature as attracted intothe bore of the solenoid to engage thereby one end of said armaturereturn spring and flex the same upwardly by the said attracting movementof said armature to render said armature return spring effective forrelease of the armature.

11. In a starting controller, an electrically energizable solenoid, anarmature attracted by energization of the solenoid, a switch forcontrolling an electric circuit including spring means urging the switchtoward closed position, said switch being normally held open by gravityapplied weight of said armature to said spring means when unattracted bythe solenoid and closed by said spring means when said armature isattracted by energization of said solenoid to remove the gravity appliedweight of the armature from the spring means, and an armature returnspring means comprising a first spring blade and a second spring bladein the form of an electric current sensitive bimetallic bladeelectrically in series with the solenoid and electrically in series withthe said switch to conduct thereby the combined currents conducted tothe said solenoid and to the circuit containing the said switch, saidfirst blade being engageable by said armature when attracted by saidsolenoid and normally disengaged from said first blade to retain saidswitch means open by gravity applied weight of the armature to thespring means for the said switch, said second blade of said returnspring means deforming under the heating effect of the combined currentsflowing through the same to spring aid thereby together with said secondblade gravity release of the armature to open said switch on decay ofcurrent flow through the solenoid and the circuit containing saidswitch.

12. Apparatus constructed and arranged in accordance with claim 11wherein said first and second blades form a short circuiting switch toshort circuit a part of the current flow through said solenoid andreduce thereby the flux effect of the solenoid on said armature, theheating effect of said bimetallic blade retaining said short circuitingswitch closed temporarily after the armature is released.

References Cited in the file of this patent UNITED STATES PATENTS1,716,389 Starr June 11, 1929 2,338,250 Logan Jan. 4, 1944 2,513,986Woodson et a1. July 4, 1950 2,711,503 Elliott June 21, 19*53 2,801,312Clark July 30, 1957 FOREIGN PATENTS 631,696 Great Britain Nov. 8, 1949

